Saturday, March 30, 2013

Ringing Tawnies

Today I had the pleasure of being invited down to March in Cambridgeshire to photograph young Tawny Owls as they were being ringed. The adult Tawnies were nesting in a purpose built 'Owl Box' set in a Walnut Tree in a large suburban garden. When I arrived the male was roosting, virtually out of sight, in an ivy-covered tree near to the house. When the sun is shining he is known to roost more in the open so as to enjoy the warmth of the sun. Not so today. The female bird was in the box keeping an eye on the three young inside. We knew that there were three young because the owners of the house and grounds have placed nest box cameras in and around the box and they keep a constant vigil on the birds. It was a proper Spring-Watch set-up.
An experienced, licenced qualified ringer from the BTO was present to ring the birds and ensure their safety. In fact everyone present seemed to be mindful of the birds' welfare above all else and the youngsters were not out of the box for more than quarter of an hour before they were safely back in their very smelly home.
The female bird meanwhile was keeping an eye on things from a thick hedge at the back of the garden.

Three sibling Tawnies -' Los Tres Amigos'

In 2010 1,716 Tawny Owls were ringed in Britain. 1,439 of these were ringed in the nest like today's birds, 65 were juveniles, that is, birds in their first calendar year and 210 were adults. The remaining two birds were un-aged as it is often difficult to tell on plumage whether a bird is in its first year or older.
In 2011 1,655 Tawny Owls were ringed; 1,458 in the nest, 44 juveniles, 148 adults and five were un-aged.
Since 1909 until the end of 2011 47,010 Tawnies have been fitted with rings.

Young Tawny Owl Strix aluco

Now here's the thing as we say: 2,550 of these have been recovered and these birds have provided some fascinating information. How old do you think a Tawny Owl can be? Ringing data suggests that they average about four years. But the average is low due to the mortality rates of young birds - only about a third manage to get through the first year of life. Lots of young, inexperienced birds are killed by traffic on the roads. But a bird ringed at Malham Tarn in North Yorks on the 25th May 1967 was found freshly dead on the 7th November 1988. It was 21 years, 5 months and 13 days old!

Young Tawny Owl showing wing in pin

Do Tawnies move about or are they faithful to one place? The bird at Malham was found close to where it was ringed so we know that it spent over 21 years cleaning up the mice and voles in the Malham Tarn area. But a nestling ringed in Torbol in the Highlands on 4th of May 1987 was hit by a car on 23rd November 1987 687 km away near Pemby Forest in Dfyed!
Two other birds have lived beyond 19 years and two more have lived to be over 20 years. Others have been recovered at distances of 202km, 205km and 217 km away from their ringing sites. All of this we know because of the successes of the BTO ringing scheme.

Young Tawny Owl
Relaxed, safe and ready for ringing

Tawny Owls lay 2 to 3 eggs and incubate for 30 days and the young fledge after a further 35 - 39 days so this pair must have laid early to mid February. In 2000 it was estimated that there were 19,000 breeding pairs of Tawny Owls in Britain. Three more have now been safely ringed and we wait to see if there is any news of them in the future.
You can check out all of the ringing information at the BTO web site here: http://www.bto.org/volunteer-surveys/ringing/ringing-scheme
Or statistics on Tawny Owls here:
http://blx1.bto.org/birdfacts/results/bob7610.htm